In recent years, speed of electric signals has been increased (frequencies of electric signals have been made higher) which are transmitted to a control printed circuit board which is embedded in an electronic device of an automobile such as a car navigation system and on which components such as an electronic component and an IC (an integrated circuit) are mounted. In addition, patterns of printed circuit boards have become denser. Generally, a high-frequency shielded cable is used to transmit such high-frequency electric signals, and along with the increase in frequencies of electric signals, demand for a high-frequency, compact shielded connector, which is connected to an end of the shielded cable, has been increased.
One type of shielded cable which is known as a coaxial cable generally has a coaxial structure which comprises: a signal wire comprising a conductor which is used as a transmission path of electric signals and composed of a plurality of metal elemental wires tied into a bundle, and an insulator covering the outer surface of the conductor; a braid defining a shielded conductor which covers the outer surface of the signal wire and is composed of a plurality of elemental wires; and an insulating sheath covering the outer surface of the shielded conductor. The shielded conductor covers the outer surface of the conductor leaving no clearance to electromagnetically shield the conductor.
Generally, a shielded connector to be connected to an end of the shielded cable which transmits high-frequency signals is provided with an inner conductor terminal to be connected to the conductor which transmits high-frequency signals, an outer conductor terminal to be connected to the shielded conductor such as the braid and arranged to cover the outer surface of the inner conductor terminal to electromagnetically shield the inner conductor terminal, and a dielectric having a predetermined dielectric constant which is provided between the inner conductor terminal and the outer conductor terminal. The inner conductor terminal and the outer conductor terminal are electronically connected to the conductor and the shielded conductor of the shielded cable respectively.
An example of a conventional shielded connector is disclosed in Japanese Patent Application Unexamined Publication No. 2005-93173. In this type of shielded connector, when connecting an inner conductor terminal and an outer conductor terminal to portions of a conductor and a shielded conductor of a coaxial cable which are exposed by stripping an insulator and a sheath, first a crimp section of the inner conductor terminal of the shielded connector is crimped onto the exposed conductor. Then, the inner conductor terminal is inserted and secured in a dielectric which is prearranged inside the outer conductor terminal of the shielded connector, and the shielded conductor is placed on a crimp section of the outer conductor terminal. The crimp section of the outer conductor terminal is then crimped onto the shielded conductor and the sheath to complete the connection.
The inner surfaces of shielded conductor crimping portions and sheath crimping portions of the outer conductor terminal according to Japanese Patent Application Unexamined Publication No. 2005-93173 are provided with reticulated knurling grooves. A braid defining the shielded conductor is pressed into the reticulated knurling grooves formed on the shielded conductor crimping portions, thereby improving fixing strength between the shielded conductor and the shielded conductor crimping portions. Similarly, the sheath is pressed into the reticulated knurling grooves formed on the sheath crimping portions, thereby improving fixing strength between the sheath and the sheath crimping portions. Generally, such reticulated knurling grooves are formed by applying press work to the outer conductor terminal before bending it.